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GI > Intro to GI physiology > Flashcards

Intro to GI physiology Flashcards

1
Q

What are the 6 basic functions of the GI tract?

A 
Ingestion
Mechanical processing
Digestion
Secretion
Absorption
Excretion
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2
Q

What does the peritoneum secrete and why?

A

Peritoneal fluid which provides lubrication and prevents friction between organs

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3
Q

What is a volvulus?

A

Bowel gets twisted and blood supply is cut off - becomes ischemic or good can’t pass

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4
Q

What is carried in the mesenteries?

A

Blood vessels
Nerves
Lymphatics

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5
Q

Why are there fat pads on the mesenteries?

A

Cushion and protect organs

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6
Q

What is the general structure of the epithelial cells in the gut?

A

Mucosa (innermost)
Submucosa - connective tissue
Musculares externa - circular muscle layer and longitudinal muscle layer that provide contraction fro peristalsis (myenteric plexus is between these two muscle layers)
Serosa - connective tissue containing a double layer of peritoneum

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7
Q

Are epithelial cells polarised? why is this important?

A

Yes

Polarised cells can target proteins to discrete parts of the cell to determine where proteins are expressed

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8
Q

What are tight junctions?

A

Near the apical surface of the cell, define apical and basolateral domain and stop proteins from mixing
Seals the gap between epithelial cells

Prevent the diffusion of plasma membrane proteins from apical to basolateral membranes of epithelial cells

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9
Q

What are occulting junctions?

A

Main bit of the tight junction - prevents stuff from passing through

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10
Q

What are adherens junctions?

A

Connects cells together by actin filaments

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11
Q

What are desmosomes?

A

Connect adjacent cells together by filaments

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12
Q

What are gap junctions?

A

Allow the passage of small water-soluble molecules from cell to cell

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13
Q

What is in between the baso-lateral membrane of the epithelial cell and the capillary network?

A

Interstitial fluid

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14
Q

What is flux?

A

Movement of molecules across the epithelium (either direction)

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15
Q

How is flux measured chemically?

A

Using radioactive isotopes as tracers

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16
Q

What causes flux?

A

Electrochemical gradients

17
Q

What is the equation for net flux of a solute?

A

Jnet = Jabs - Jsec

Jnet = net flux
Jabs = absorptive flux
Jsec = secretory flux
18
Q

What are the two routes for absorption from the lumen into the blood?

A

Transcellular (through cells)

Paracellular (between cells)

19
Q

What is secondary active transport?

A

Energy to drive active transport comes from the electrochemical gradient from one substrate (using primary active transport), and the second substrate then moves against its electrochemical gradient

20
Q

What cellular route must active processes use for absorption?

A

Transcellular

21
Q

Which route of absorption can water use?

A

Both paracellular and transcellular

22
Q

What channels does water move through to get across plasma membranes?

A

Aquaporin channels

23
Q

What type of nerves supply the main sensory and motor control of GI activity?

A

Parasympathetic

24
Q

What nerve controls the forget and midgut derivatives?

A

Vagus

25
Q

What nerve controls the hindgut components of the GI tract?

A

Pelvic splanchnic nerves

26
Q

What is the enteric nervous system?

A

Motor and sensory neurons (autonomic) in two interconnected plexuses (myenteric and submucosal) in the walls of the GI tract - these neurons control the coordinated contraction and relaxation of intestinal smooth muscle and regulate secretion and blood flow. Thousands of small ganglia that lie within the walls of the GI tract organs.

Generally independent of CNS, but does receive input from sympathetic nerves

27
Q

What modulates the enteric nervous system?

A

ANS

28
Q

Where is the myenteric plexus of the enteric nervous system located?

A

Between the circular muscle and longitudinal muscle layer in the musclaris externa

29
Q

Where is the submucosal plexus of the enteric nervous system located?

A

Between the submucosa and the circular muscle layer

30
Q

What are slow waves?

A

Regular periodic depolarisations in the resting membrane potential of cells that makes it easier for a small signal to initiate a contraction/action potential. They set the timing for when contraction MAY occur.
(a neural or hormonal signal will ONLY initiate activity during a slow wave)

31
Q

What regulates slow waves?

A

Myenteric and submocsal plexi

32
Q

How often do slow waves occur?

A

3-12min-1

33
Q

What is the role of interstitial cells of Cajal?

A

Mediate slow waves (pacemaker cells)

Facilitate communication between nervous system and smooth muscle. Cause contraction in a rhythmic and coordinated fashion - peristalsis.

GI (10 decks)

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